KR20120102280A - A sodium-free flux for removing magnesium impurity from molten aluminium or aluminium alloy and the removing method of magnesium impurity from molten aluminium or aluminium alloy using the same - Google Patents

Abstract

PURPOSE: A sodium-free flux for removing magnesium impurity from molten aluminium or aluminium alloy and a method of removing magnesium impurity from molten aluminium or aluminium alloy using the same are provided to control the reaction heat of a flux by using two or more kinds of sodium-free metal fluoride as main components. CONSTITUTION: A sodium-free flux for removing magnesium impurity from molten aluminium or aluminium alloy comprises 60-100 weight% of a eutectic mixture of sodium-free metal fluoride which contains different two kinds of sodium-free metal fluoride. The melting point of the first or/and second sodium-free metal fluoride is 800 °C or higher, and the melting point of the eutectic mixture is 700 °C or lower. The metal fluoride of the eutectic mixture includes two or more selected from the group consisting of AlF3, KAlF4, K2AlF5, K3AlF6, KF, and K2SiF6.

Description

Non-Sodium Flux for Magnesium Impurity Removal in Aluminum or Aluminum Alloy Molten Metal and Mg Impurity Removal Method for Magnesium Impurity in Aluminum or Aluminum Alloy Molten Metal FROM MOLTEN ALUMINIUM OR ALUMINIUM ALLOY USING THE SAME}

The present invention relates to a non-sodium flux that is treated to remove magnesium from an aluminum or aluminum alloy melt containing magnesium impurities and a method for removing magnesium from an aluminum or aluminum alloy melt using the same.

Aluminum is a metal that is used as a high strength, high corrosion resistance alloy with various kinds of elements such as Si, Mg, Zn, Mn, Cu as well as being light and good processability, high electric and thermal conductivity. Accordingly, aluminum or aluminum alloys are widely used in industries such as beverage cans, vehicles, household appliances, construction, machinery, electricity, and aircraft.

Aluminum is high in price, and the energy required for aluminum regeneration is as low as 3 to 5% of the energy required for primary metal production. The production rate of secondary metals produced by the addition of elements is increasing.

In particular, the need for regeneration of aluminum or aluminum alloys containing magnesium is becoming increasingly important. For example, aluminum waste cans (UBCs) are used in large quantities as raw materials for aluminum scrap. The use of aluminum waste cans as aluminum scraps can greatly reduce the production cost of aluminum secondary now. Materials such as aluminum waste cans contain a large amount of magnesium not only in the body but also in the lid and tab, so that the magnesium content is below a certain amount. It needs to be adjusted. In order to solve this problem, a method of diluting the content of magnesium by adding high-purity aluminum as in the present day has been used, but this offsets the advantage of using aluminum waste cans.

Therefore, a flux treatment method for removing magnesium components in the molten metal during the regeneration of aluminum and aluminum alloy has been proposed.

Japanese Patent Application Laid-Open No. 61-119630 discloses a method for removing magnesium by adding molten flux consisting of 35-45% by weight of NaCl, 35-45% by weight of KCl, and 15-25% by weight of AlF ₃ to a molten aluminum or aluminum alloy scrap. Is disclosed.

The above-mentioned prior art technique uses a flux containing 70-90% by weight of metal chlorides to selectively remove the magnesium element in the molten aluminum. However, metal chlorides such as NaCl and KCl have low reactivity with magnesium, resulting in poor removal efficiency. As a result, the amount of flux is increased. That is, in order to increase the removal efficiency of magnesium, the weight ratio of the flux to the weight of the scrap should be used more than 1.0, the purpose of reducing the manufacturing cost due to the use of scraps, such as aluminum cans are greatly impaired. In addition, since the flux of the prior document has to be introduced in a large amount in the melting furnace in the molten state, the energy consumption increases, there is a problem that causes corrosion of the melting furnace.

In addition, sodium-based fluxes containing sodium elements such as NaCl and Na ₂ SiF ₆ are widely used as flux components used in dissolving aluminum. However, even though aluminum molten metal contains only a few ppm of sodium element, it causes grain boundary brittleness due to metal corrosion, and sodium element reacts with moisture in the air to generate hydrogen gas, which causes pinhole defects in aluminum molded products. As a result, the oxidation of aluminum on the surface of the molten metal is accelerated, and the amount of dross is rapidly increased.

The problem to be solved by the present invention is to solve the above problems, there is no problem caused by the use of flux components containing sodium element, high removal efficiency for magnesium effectively remove magnesium in the molten metal in a relatively small amount Non-sodium flux for removing magnesium impurity in aluminum or aluminum alloy molten metal that can be economical and has a melting point lowered below the melt temperature and does not need to be separately melted and a method for removing magnesium impurity in aluminum or aluminum alloy molten metal using the same To provide.

Non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention,

60 to 100 wt% of a eutectic mixture of a first non-sodium metal fluoride and a non-sodium metal fluoride including the first non-sodium metal fluoride and another second non-sodium metal fluoride,

At least one of the first non-sodium metal fluoride and the second non-sodium metal fluoride has a melting point of 800 ° C. or more and a melting point of the eutectic mixture of 700 ° C. or less.

In the non-sodium flux for removing magnesium impurities in molten aluminum or aluminum alloy according to the present invention, the eutectic mixture of the non-sodium metal fluoride is AlF ₃ , KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , KF and K It is preferably a eutectic mixture of at least two or more non-sodium based metal fluorides selected from the group consisting of ₂ SiF ₆ . In particular, the first first non-sodium metal fluoride is AlF ₃ , the second non-sodium metal fluoride is at least selected from the group consisting of KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , KF and K ₂ SiF ₆ It is preferred that it is at least one non-sodium metal fluoride. At this time, the content of AlF ₃ is more preferably 20% by weight or more based on the total weight of the eutectic mixture of non-sodium metal fluoride.

Non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention further comprises at least one selected from the group consisting of potassium carbonate, potassium sulfate and potassium nitrate in an amount of 10% by weight or less based on the total weight of the flux. It is preferable.

In addition, the non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention preferably further comprises non-sodium chloride at 40 wt% or less based on the total weight of the flux. KCl, AlCl ₃ , NH ₄ Cl, C ₂ Cl ₆ (Hexachloroethane) and the like can be used alone or two or more thereof.

In addition, the method for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention,

(S1) preparing a molten metal maintained at 700 to 800 ° C by melting aluminum or an aluminum alloy containing magnesium impurities;

(S2) injecting a non-sodium flux for removing magnesium impurities of the above-described composition into the molten metal;

(S3) removing the dross of the surface of the molten metal from the resultant of (S2).

In the magnesium impurity removing method in the aluminum or aluminum alloy molten metal according to the present invention, the step of introducing the magnesium impurity removing flux of (S2) is to spread the non-sodium-based flux for removing magnesium impurities on the surface of the molten metal or inert gas Together with a non-sodium flux for removing magnesium impurities into the molten metal through a pipe.

Since the non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention does not contain sodium element, it does not involve the problem of using sodium flux.

In addition, the non-sodium flux according to the present invention is economical because it can effectively remove magnesium in the molten metal in a relatively small amount due to high removal efficiency for magnesium. In addition, since the melting point of the eutectic mixture consisting of two or more non-sodium-based metal fluoride as the main component is lowered below the melt temperature, it is not necessary to melt the flux separately and does not affect the durability of the furnace. In addition, there is an advantage that the reaction heat of the flux can be controlled by using two or more non-sodium metal fluorides.

Thus, using the non-sodium flux of the present invention, it is possible to economically and easily remove magnesium impurities in the aluminum or aluminum alloy molten metal.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

The non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention is a flux composed of a component containing no sodium element. As described above, the non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention does not include a sodium element, and thus does not involve the problem of using sodium flux.

The non-sodium flux of the present invention contains from 60 to 100% by weight of non-sodium metal fluoride. Non-sodium-based metal fluorides have much higher reactivity with magnesium than metal chlorides such as NaCl and KCl, so the removal efficiency of magnesium is very good. Therefore, magnesium in the molten metal can be effectively removed even in a relatively small amount of the flux mainly composed of metal chlorides, resulting in high economic efficiency. If the content of non-sodium-based metal fluoride is less than 60% by weight based on the total weight of the flux, the amount of flux to be added for magnesium removal may increase, thereby lowering economic efficiency. For example, look at the reaction scheme where K ₃ AlF ₆ is removed by fluorinating magnesium.

[Reaction Scheme 1]

Al + K ₃ AlF ₆ → 2AlF ₃ + 3K

2AlF ₃ + 3Mg → 3MgF ₂ + 2Al

In addition, the non-sodium-based metal fluorides included as flux in the present invention include two or more different kinds of non-sodium-based metal fluorides, and these non-sodium-based metal fluorides form a eutectic mixture. That is, the non-sodium metal fluoride used in the present invention includes a first non-sodium metal fluoride and a second non-sodium metal fluoride different from the first non-sodium metal fluoride and become an eutectic mixture. . As such, the eutectic mixture of two or more different non-sodium metal fluorides has a lower melting point. The molten aluminum is usually maintained at 700 to 800 ° C. Since the melting point of the non-sodium metal fluoride is often 800 ° C or higher, it is necessary to separately melt the aluminum molten metal in order to treat it with flux. This increases energy consumption and causes oxidation of the molten aluminum and corrosion of the furnace. In the present invention solves this problem by using two or more non-sodium-based metal fluoride to form a eutectic mixture, the melting point of which can be lowered to a temperature below the melt. That is, at least one of the first non-sodium metal fluoride and the second non-sodium metal fluoride has a melting point of 800 ° C. or higher, which is higher than the temperature of the molten metal, but they form a eutectic mixture and the melting point of 700 ° C. or less (preferably 680 ° C.). Drop). As a result, the flux does not need to be separately melted. In addition, by using two or more kinds of non-sodium metal fluoride to enhance the heat of reaction of the flux to increase the energy efficiency according to the temperature of the molten metal, it is also possible to control the reaction rate.

Non-sodium metal fluorides include AlF ₃ (Aluminium fluoride, melting point 1040 ℃), KAlF ₄ (Potassium Cryolite, melting point 560 ℃), K ₃ AlF ₆ (Potassium Cryolite, melting point 1025 ℃), K ₂ AlF ₅ (Potassium Cryolite, Melting point 680 ° C.), KF (Potassium Fluoride, melting point 860 ° C.), K ₂ SiF ₆ (Potassium fluorosilicate, 475 ° C. decomposition), and the like, and the eutectic mixture of the non-sodium metal fluoride includes at least two or more ratios selected from them. It is preferably a eutectic mixture of sodium-based metal fluorides.

In particular, the first non-sodium metal fluoride is AlF ₃ , the second non-sodium metal fluoride is at least one selected from the group consisting of KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , KF and K ₂ SiF ₆ It is preferable that it is a non-sodium type metal fluoride. When AlF ₃ is included, as shown in Scheme 1, the reaction with magnesium in the molten aluminum is accelerated, thereby improving the magnesium removal performance.

At this time, the content of AlF ₃ is more preferably 20% by weight or more, more preferably 70% by weight or less based on the total weight of the eutectic mixture of the non-sodium metal fluoride.

On the other hand, the non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention further comprises at least one selected from the group consisting of potassium carbonate, potassium sulfate and potassium nitrate to 10% by weight or less based on the total weight of the flux. It is preferable to include. These additives improve the reaction persistence of eutectic mixtures of non-sodium based metal fluorides. It also has the function of lowering the melting point of the flux.

In addition, the non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy according to the present invention preferably further comprises non-sodium chloride at 40 wt% or less based on the total weight of the flux. These non-sodium chlorides control the rate of reaction between the eutectic mixture of non-sodium-based metal fluoride and magnesium to help sustain a continuous reaction. As non-sodium chloride, KCl, AlCl ₃ , NH ₄ Cl, C ₂ Cl ₆ (Hexachloroethane), etc. may be used alone or in combination of two or more thereof.

By using the non-sodium flux for removing magnesium impurities in the molten aluminum or aluminum alloy described above, magnesium impurities in the aluminum or aluminum alloy molten metal can be removed by the following method.

First, by melting the aluminum or aluminum alloy containing magnesium impurities to prepare a molten metal maintained at 700 to 800 ℃ (step S1).

Aluminum or aluminum alloys containing magnesium impurities can be used in addition to aluminum cans, as long as they contain magnesium and need to be removed. Since the melting temperature of aluminum is 660.32 ° C., the inside of the melt is maintained at 700 to 800 ° C. so that the aluminum or aluminum alloy is completely melted.

Subsequently, in the molten metal, a non-sodium flux for removing magnesium impurities, that is, a non-sodium flux including a eutectic mixture of a predetermined non-sodium metal fluoride is added (step S2).

As a method of injecting non-sodium flux for removing magnesium impurities, a conventional flux input method of injecting non-sodium flux into a molten aluminum or aluminum alloy may be used. For example, magnesium impurities may be removed from the surface of the molten metal. It can be made by spreading the molten non-sodium flux or by blowing a non-sodium flux for removing magnesium impurities together with an inert gas into the molten metal through a pipe. In the case of removing magnesium from the molten aluminum using the non-sodium flux of the present invention, the addition amount may be appropriately selected in consideration of the type of aluminum, the amount of molten metal, the melt temperature, and the like. Non-sodium flux may be added at a weight of ˜6 times.

The injected non-sodium flux reacts with magnesium in the melt to form magnesium fluoride. Dross containing magnesium fluoride migrates to the surface of the melt due to the difference in specific gravity. Therefore, by removing the dross on the surface of the molten metal (step S3), magnesium impurities can be removed from the molten metal.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the following examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example 1

5 tons of a mixture of ADC12 grade aluminum scrap and aluminum waste caps (UBCs) were melted in a melting furnace, and then a non-sodium flux was prepared to produce Al secondary porcelain (magnesium content of less than 0.3% by weight) meeting KS ALDC12 specification. Was treated by adding.

The initial concentration of magnesium in the molten metal, the specific non-sodium flux composition, the flux treatment method and the like are shown below.

Initial Mg Concentration in Melt: See Table 1

Melting Furnace: 5ton Reflective Melting Furnace

Melting Temperature: 720 ~ 750 ℃

Flux: 40 parts by weight of AlF ₃ and 60 parts by weight of K ₃ AlF ₆

Flux throughput: 10 kg

Flux treatment method: After spreading the flux on the molten surface, tap the flux surface using a forklift skimmer

Flux processing time: 25 minutes

Table 1 shows the measurement results of the magnesium removal rate in the molten metal after the flux treatment.

Example 2

The flux was treated in the same manner as in Example 1 except that the flux was injected into the molten metal at a rate of 1.5 kg / min using nitrogen gas instead of dispersing the flux on the molten surface.

Example 3

The same procedure as in Example 1 was carried out except that 40 parts by weight of AlF _3, 40 parts by weight of K ₃ AlF ₆ and 20 parts by weight of KCl were used as the flux.

Example 4

The same process as in Example 1 was carried out except that 45 parts by weight of AlF _3, 45 parts by weight of K ₃ AlF ₆ and 10 parts by weight of KCl were used as the flux.

Example 5

The same process as in Example 1 was carried out except that a mixture of 65 parts by weight of AlF ₃ , 15 parts by weight of K ₃ AlF _6, 15 parts by weight of KCl, and 5 parts by weight of K ₂ SO ₄ was used.

Example 6

The same procedure as in Example 1 was carried out except that a mixture of 60 parts by weight of AlF ₃ , 20 parts by weight of KAlF ₄ , 5 parts by weight of K ₂ SiF ₆ , 10 parts by weight of KCl and 5 parts by weight of K ₂ CO ₃ was used.

Example 7

The same procedure as in Example 1 was carried out except that a mixture of 65 parts by weight of AlF ₃ , 25 parts by weight of K ₃ AlF ₆ and 10 parts by weight of KCl was used as the flux.

Example 8

Example ₁ except that a mixture of 60 parts by weight of AlF _{3 and} 40 parts by weight of Potassium Cryolite mixture (commercialized mixture of KAlF ₄ , K ₂ AlF ₅ and K ₃ AlF ₆ , melting point 600-680 ° C.) It carried out similarly.

Example 9

The same process as in Example 1 was carried out except that 65 parts by weight of AlF ₃ , 25 parts by weight of Potassium Cryolite mixture, and 10 parts by weight of KCl were used as the flux.

Comparative Example 1

The same procedure as in Example 2 was carried out except that 40 parts by weight of NaCl, 40 parts by weight of KCl, and 20 parts by weight of AlF ₃ were used as the flux.

Referring to the results of Table 1, Examples 1 to 9 are Al secondary secondary (magnesium content 0.3 wt%) to satisfy the specifications of KS ALDC12 by removing a large amount of magnesium impurities by treating the non-sodium flux of the composition according to the present invention It can be seen that less than%)). On the other hand, Comparative Example 1 can be seen that the removal efficiency of magnesium impurities is significantly lower than the embodiments.

Claims (9)

60 to 100 wt% of a eutectic mixture of a first non-sodium metal fluoride and a non-sodium metal fluoride including the first non-sodium metal fluoride and another second non-sodium metal fluoride,
At least one of the first non-sodium metal fluoride and the second non-sodium metal fluoride has a melting point of 800 ° C. or more and a melting point of the eutectic mixture of 700 ° C. or less, wherein the ratio of removing magnesium impurities in an aluminum or aluminum alloy melt is Sodium flux. The method of claim 1,
The eutectic mixture of the non-sodium metal fluoride is an eutectic mixture of at least two or more non-sodium metal fluorides selected from the group consisting of AlF ₃ , KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , KF and K ₂ SiF ₆ Non-sodium flux for removing magnesium impurities in an aluminum or aluminum alloy molten metal, characterized in that. The method of claim 1,
The first non-sodium metal fluoride is AlF ₃ , the second non-sodium metal fluoride is at least one selected from the group consisting of KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , KF and K ₂ SiF ₆ Non-sodium flux for removing magnesium impurities in an aluminum or aluminum alloy molten metal, characterized in that the non-sodium metal fluoride. The method of claim 3,
The content of the AlF ₃ is 20% by weight or more based on the total weight of the eutectic mixture of non-sodium-based metal fluoride non-sodium flux for removing magnesium impurities in the aluminum or aluminum alloy molten metal. The method of claim 1,
Non-sodium flux for removing magnesium impurities in an aluminum or aluminum alloy molten metal, characterized in that it further comprises at least one selected from the group consisting of potassium carbonate, potassium sulfate and potassium nitrate to 10% by weight or less based on the total weight of the flux. The method of claim 1,
Magnesium impurity removal flux in the aluminum or aluminum alloy molten metal, characterized in that it further comprises 40% by weight or less of non-sodium chloride based on the total weight of the flux. The method of claim 6,
The non-sodium chloride is at least one non-sodium chloride selected from the group consisting of KCl, AlCl ₃ , NH ₄ Cl and C ₂ Cl ₆ Flux for removing magnesium impurities in the aluminum or aluminum alloy molten metal. (S1) preparing a molten metal maintained at 700 to 800 ° C by melting aluminum or an aluminum alloy containing magnesium impurities;
(S2) injecting a non-sodium flux for removing magnesium impurities of any one of claims 1 to 7 in the molten metal;
(S3) A method for removing magnesium impurities in an aluminum or aluminum alloy molten metal, comprising the step of removing dross from the surface of the molten metal from the resultant of (S2). The method of claim 8,
Injecting the non-sodium-based flux for removing magnesium impurities in (S2) is to spread the non-sodium-based flux for removing magnesium impurities on the surface of the molten metal or pipe the non-sodium-based flux for removing magnesium impurities with an inert gas Magnesium impurity removal method in the aluminum or aluminum alloy molten metal, characterized by the method of blowing into the molten metal through.